1. Field
Aspects of the present general inventive concept relate to encoding and decoding multi-channel audio signals, and more particularly, to a method and apparatus which encode multi-channel audio signals, in which a residual signal that may improve sound quality of each channel when restoring the multi-channel audio signals is used as predetermined parametric information, and a method and apparatus which decode the encoded multi-channel audio signals by using the encoded residual signal.
2. Description of the Related Art
In general, methods of encoding multi-channel audio signals can be roughly classified into waveform audio coding and parametric audio coding. Examples of waveform encoding include moving picture experts group (MPEG)-2 multi-channel (MC) audio coding, Advanced Audio Coding (AAC) MC audio coding, Bit-Sliced Arithmetic Coding (BSAC)/Audio Video Standard (AVS) MC audio coding, and the like.
In parametric audio coding, an audio signal is divided into frequency components and amplitude components in a frequency domain, and information about such frequency and amplitude components are parameterized in order to encode the audio signal by using such parameters. For example, when a stereo-audio signal is encoded using parametric audio coding, a left-channel audio signal and a right-channel audio signal of the stereo-audio signal are downmixed to generate a mono-audio signal, and then the mono-audio signal is encoded. In addition, parameters, such as an interchannel intensity difference (IID), an interchannel correlation (ID), an overall phase difference (OPD), and an interchannel phase difference (IPD), are encoded for each frequency band. Herein, the IID and ID parameters are used to determine the intensities of left-channel and right-channel audio signals of stereo-audio signals when decoding. In addition, the OPD and IPD parameters are used to determine the phases of the left-channel and right-channel audio signals of the stereo-audio signals when decoding.
In such parametric audio coding, an audio signal decoded after being encoded may differ from an initial input audio signal. In general, such a difference value between the audio signal restored after being encoded and the input audio signal is defined as a residual signal. Such a residual signal represents a sort of encoding error. In order to improve sound quality of each channel when decoding an audio signal, the residual signal has to be decoded for use when decoding the audio signal.